First of all get a box of coloured crayons and without looking at them , pick one, and hold it behind your he … ad. It exerts fluid pressure that keeps the retina layers pressed together to maintain the shape of the eye and to maintain sharp focus of images on the retina. From here the fluid drains through the lacrimal canals into the lacrimal sac. They exercise control over the size of the pupil, and they lead to acute suppression of secretion by the. Make sure you don't see it yet! The medial rectus muscle, for example, pulls the eyeball medially, as if to look at the nose. The process through which these proteins go is quite similar — upon being subjected to of a particular wavelength and intensity, the protein breaks down into two constituent products.
Sclera: The tough outer coat that protects the entire eyeball. Diagram of the different layers of the eyeball Outer Layer The outer fibrous layer maintains the shape of the eyeball and protects more fragile internal structure. In the human eye, light enters the pupil and is focused on the retina by the lens. Vitreous humour The vitreous humour is a transparent jelly-like fluid that fills the posterior chamber. It is yellowish in colour, and highly pigmented. The ganglion cell nuclei migrate radially outwards in a circle, leaving the fovea free of ganglion cell nuclei.
Some aquatic animals have a second eyelid in each eye which refracts the light and helps them see clearly both above and below water. The macula contains a depression called the fovea, which has a high concentration of light detecting cells. If the drainage of aqueous humor is obstructed, a condition known as glaucoma can result. Vitreous: Clear jelly-like substance that fills the eye from the lens to the back of the eye. Together with the lens, the cornea is responsible focussing light on the retina.
In this manner, it can control the amount of light entering the eye. When stimulated by light, retinal photoreceptor cells send signals to neighbouring cells in the retina that then relay the signals through the to the visual centres of the. The sclera is white, opaque, and hard. Zonules The zonule also known as suspensory ligaments is a ring of small fibres that hold the lens suspended in place. These drain into the cavernous sinus, a dural venous sinus in close proximity to the eye. Clinical Relevance: Papilloedema Papilloedema refers to swelling of the optic disc that occurs secondary to raised intracranial pressure. The anterior chamber is filled with a watery, nutrient rich fluid known as the aqueous humor which is produced by the ciliary processes of the ciliary body.
A disease called pericarditis occurs when this fibrous sac becomes inflamed. This causes fluid to extravasate from blood vessels and collect in the retina, producing a swollen optic disc. However, being a soft organ that is essentially a protrusion of neural tissue, the eye has to be equipped with all the additional features that will ensure that it can remain operational and intact. The Outer Layer The outer layer contains the sclera the white of the eye and the cornea the clear dome at the front of the eye. The posterior segment is filled with a gelatinous substance known as the vitreous humor. Central Artery and Vein The central artery and vein runs through the center of the optic nerve.
The eye is the organ responsible for vision. If the eyeball is punctured and vitreous humor is lost, the retina may fall away from the choroid; this is one possible cause of a detached retina. The retina contains nerve cells that transmit signals from the retina to the brain. The human eye has three layers of eye tissue: the fibrous layer, the vascular layer, and the. Broadly, the retina can be divided into the neural layer that has light receptors and deciphers the light stimuli and the pigmented area that absorbs light so that it does not reflect on the neural layer and create distortion.
The rods and cones enable vision. The final portion of the sensory retina to mature is the fovea, where the ganglion cell layer thickening begins during midgestation. The fovea, which contains only cones, is a small depression in the macula and is the area for best color vision. The fibrous layer has two distinct parts. Cones enable us to detect color while rods enable us to see in poor light.
Posterior Chamber The posterior chamber is a larger area than the anterior chamber. The first two chambers are filled with aqueous humor whereas the vitreous chamber is filled with a more viscous fluid, the vitreous humor. The Inner Layer The inner layer of the eye, or retina, is similar to film in a camera. The posterior segment is the back five-sixths of the that includes the and all of the optical structures behind it: the , , , and. Sclera The sclera is outermost layer of the eyeball. So on February 14th, look into your Valentine's eyes — chances are his or her pupils will be dilated! Light rays are focused through the transparent cornea and lens upon the retina.
The iris is the part of the vascular layer of eye tissue that determines a person's eye color. Much of the eye's pigment is located in the vascular layer of eye tissue. Lingering eye contact also is a strong indicator for a potential love match. In the following chapters, we will describe in greater detail the individual nerve cells that make up the retina and the functional pathways into which these neurons are organized. However, unlike the , the shape and focusing power of the cornea are not adjustable.
It is situated between the lens and the cornea. The sclera gives the eye most of its white color. This is accomplished mainly by changing the curvature of the lens. It covers most of the outer surface of the eyeball. Here a maximally focussed image initiates resolution of the finest detail and direct transmission of that detail to the brain for the higher operations needed for perception. Tear drains from the eyes in to the nose through the tear duct. The aqueous humour is produced by the ciliary body.